1. Field of the Invention
The present invention relates to the field of archery. Specifically, the invention relates to the vanes or fletching found on arrow devices.
2. Description of the Prior Art
Bowhunting and archery rely on arrows to have two key properties. First, arrows must achieve penetration of the intended target regardless of whether that intended target is a static bulls-eye or a hunted animal. Second, arrows must fly straight and true. Even the most skilled of archers, with the most trained eyes, can not compensate for an arrow that can not find its intended mark. These two great needs are somewhat at odds with one another. Historical solutions have sought to balance these two needs in order to minimize the detrimental effects of each while maximizing the overall result.
The problem of target penetration has been addressed in several ways. Target penetration can be directly correlated to the likelihood of hunting success: an arrow that can not adequately penetrate an intended animal is of little use to a hunter. The overall mass of the arrow could be increased, but more massive arrows are clumsy and must be fired in a high arc to reach the intended target. Simple xe2x80x9cfield pointxe2x80x9d arrow tips can provide adequate penetration for targets in competition, but they are not very effective for killing hunted animals. Prior art broadhead arrows were invented to increase effective hunting penetration and success potential. Typically two to four flat, triangular blades are arranged around the forward pointed tip. As the tip enters the intended target, the blades slice a region much greater than the diameter of the arrow shaft. Unfortunately, these broad, flat blades have a pronounced aerodynamic effect that can radically affect the overall stability of the arrow in flight and significantly reduce the precision of flight. Since the majority of hunting tips are broadhead in design, the combined effect of broadhead and fins at opposite ends of an arrow may not promote a stable flight.
Simple fletching, or other guidance fins, were added to the aft end of prior art arrows. Typically, two to four fins are applied parallel to the long axis of the arrow surrounding the aft end. As the arrow sails through the air, these fins are intended to straighten the overall flight path by effectively pushing the tip of the arrow in the right direction. Prior art, commercially available arrows, also teach applying the fins in a slightly helical or off-main axis manner to the arrow shaft. Such an arrow spins, once released, in order to promote a truer flight. However, these same fins typically account for sixty percent of the overall aerodynamic drag experienced by the arrow in flight. Fins of reduced size have less drag but also provide less overall stability. Minimizing drag is important to increase overall range and speed at impact. Virtually all prior art arrow vanes are constructed of materials which flex or bend when the arrow is first released due to aerodynamic forces. As a result they fold almost flat when the arrow is released and do not apply sufficient torque to the arrow to bring it to a speed of rotation adequate to ensure stability until significant deviation from the initial course has occurred. The only prior art vanes which are constructed of rigid plastic either have very high aerodynamic drag due to sharp projecting angles or are incompatible with a standard arrow rest.
The present invention is a system of arrow vanes that provide excellent main shaft rotation without producing a large amount of aerodynamic drag. A plurality of modest vanes are attached around the aft end of any conventional arrow shaft or integral to the aft end of any conventional arrow shaft. The invention is compatible with all contemporary arrow shafts.
A key feature of the current invention is that each vane constitutes an airfoil, with the airfoils together acting as an axial flow turbine, to maximize the twisting force or torque applied to the arrow while simultaneously minimizing aerodynamic drag at both low and high rates of rotation. To achieve this, the airfoil is a curved surface, like the wing of an aircraft, and also varies in pitch from zero at the base to a maximum pitch at the tip, which may be as great as 30 degrees. When the arrow is rotating rapidly, the portion of the vane near the tip is moving through the air in a spiral path. The gradual variation in pitch along the length of the vane ensures that the portion of the vane near the tip is aligned along the path it follows through the air, minimizing drag. This same principle of changing pitch with radial distance is well established in the design of aircraft propellers and turbines, but has never been applied to the design of arrow vanes.
In the present invention, the geometry of each vane constitutes an airfoil wherein the leading edge of each vane is parallel to the long axis of the arrow shaft, and the trailing edge of each vane is deflected out of the plane of the vane like an airfoil. All vanes of the present invention are identical with all deflected portions facing the same direction when the arrow is viewed down its long axis. In flight, the arrow rotates as a result of airflow over the deflected portion of the vanes much as the control surface on an aircraft wing changes the direction of the aircraft if said control surface is deflected out of the major plane of the aircraft wing.
Another key feature of the present invention is one or more vents in the vane surface. Careful placement of these vents decreases aerodynamic drag upon initial release from a bow and also once rotational speed is achieved.